Generally, an IC device may include a variety of components and elements such as transistors, diodes, contacts, capacitors, inductors, or the like, which may provide various functionalities in operation of an IC device. Some IC devices may be based on SOI technology where the components of the IC device are formed in a silicon (Si) layer above the insulator (e.g., buried-oxide (BOX)) layer, which may provide a good isolation from a Si substrate for the IC device. SOI based devices commonly include protection diodes (e.g., connecting to a gate of a transistor) and back-plate (BP) or transistor well contacts (e.g., for backside biasing for tuning threshold voltage of a component in the IC device). In some scenarios, n-type or p-type BPs and wells under SOI transistors may be formed by implantation of n-type or p-type dopant species selectively (e.g., by lithography/mask steps). Deep and/or shallow trench isolation regions may be formed to isolate adjacent well-to-well and/or BP-to-BP areas, respectively.
FIG. 1 schematically illustrates an example circuit in an IC device including a protection diode 101 connected to a metal gate line (or a polysilicon gate line) 103 of a transistor 105. The transistor on SOI substrate is separated from its BP 107 vertically by a BOX layer 109. The diode can provide protection against electrical charge (e.g., during fabrication processes or from the external environment of an IC device via its input/output elements) that may accumulate at the gate 111 of the transistor causing damage. However, for SOI technology, devices (e.g., transistors) are on the SOI layer and isolated from the Si substrate by the BOX layer. Standard P-N junction based diodes cannot serve as protection diodes as they are on the BOX layer and cannot release accumulated electrical charge to the Si substrate. Moreover, implementing the contacts to BP or well or formation of a diode in a well may require extra lithography steps as well as more complex processes (e.g., etching through the BOX layer, implants for forming diode junctions or contacts to the Si substrate), special contact formation schemes (e.g., through a trench silicide (TS)/active area contact (CA)/gate contact (CB)), and a large layout area for circuit implementation that may impact fabrication time, cost, and reliability of an IC device.
Therefore, a need exists for a methodology enabling efficient connection to substrate contacts or diode junctions in SOI based devices and resulting devices.